code: def test_cm_paired_paths():
      cm = TextFileContentsManager()
      cm.paired_notebooks = dict()
  
      three = "ipynb,py,md"
      cm.update_paired_notebooks("nb.ipynb", three)
      assert cm.paired_notebooks == {
          "nb." + fmt: (fmt, three) for fmt in three.split(",")
      }
  
      two = "ipynb,Rmd"
      cm.update_paired_notebooks("nb.ipynb", two)
      assert cm.paired_notebooks == {
          "nb." + fmt: (fmt, two) for fmt in two.split(",")
      }
  
      one = "ipynb"
      cm.update_paired_notebooks("nb.ipynb", one)
      assert cm.paired_notebooks == {}
  
      zero = ""
      cm.update_paired_notebooks("nb.ipynb", zero)
      assert cm.paired_notebooks == {}
  
imports: import os
  import unittest.mock
  import pytest
  import jupytext
  from jupytext.cli import jupytext
  from jupytext.compare import compare
  from jupytext.contentsmanager import TextFileContentsManager
  from jupytext.formats import long_form_multiple_formats, long_form_one_format, short_form_multiple_formats
  from jupytext.paired_paths import InconsistentPath, base_path, full_path, paired_paths
label_desc: Use image node_id 19 for calling a global function with example usage: test_cm_paired_paths() without return types